Grain drier



Nov. 2, 1943. G. J. BURKHARDT GRAIN DRIER Filed Feb.

12, 1941 2 Sheets-Sheet l grwe wbo'n 13-1- EURKHARDT 1943. G. J.BURKHAIRD'IH GRAIN DRIER 1941 '2 Sheets-Sheet 2 Filed Feb. 12

E J .EJURKHARD TI Patented Nov. 2, 1943,

ur OFFICE.

George J. Burkhardt, Riverdale, Md. Application February 12, 1941,Serial No. 378,508

(Granted under the act of March 3, 1883, as amended April 30, 1928; 3700. G. 757) 1 Claim.

This application is made under the act of March 3, 1883, as amended bythe act of April 30, 1928, and the invention herein'described andclaimed, if patented, may be manufactured and used by or for theGovernment of the United States of America for governmental purposeswithout the payment to me of any royalty thereon.

My invention relates to apparatus for drying grain. It is well knownthat grains of various kinds vary considerably with regard to the amountof moisture contained at the time of harvesting, the actual percentageof moisture varying with the kind of grain and, more particularly,according to weather conditions obtained during and immediatelypreceding the period of harvesting. It is well understood by grainhandlers generally, that grain having too high a moisture content cannotbe safely held in bulk storage for any length of time owing to thetendency of such grain to become self-heating when so stored.

Heating of stored grain may occur through either.

the rapid germination of mould spores which are carried along with thegrain and become active under appropriate conditions of moisture andtemperature, or may occur through metabolic processes taking placewithin the grain kernels themselves, which processes are materiallyaccelerated by the presence of excessive moisture in the grain. Thetemperature rise of the grain, resulting from either of these processes,or both in combination, is at first gradual, but becomes more pronouncedas the grain temperature increases, the process being self-accelerating,and sooner or later results in a rapid increase of the temperature tovalues at which rancidity and mustiness quickly develop, together withmore or less complete loss of germinating power, all of which markedlydepreciate the value of the grain.

The only practicable means so far found of keeping such grain in soundcondition is the reduction, by drying, of the moisture content of thegrain to a value at which it will be stable in bulk storage. Variousmeans and methods of drying grain have been used but drying apparatushitherto employed have been unsuited to farm use. by reason of being toocumbersome and costly, or, if constructed of small size, were either ofinadequate grain handling capacity or incapable of removing moisture ata suiliciently rapid rate.-

My invention provides a grain drying apparatus of simple and compacttype and of moderate cost and relatively high grain drying capacity inpro portion to its size and weight, capable of effecting a pronouncedreduction in moisture content with a single pass of the grain throughthe apparatus, drying being efiected at a high thermal efficiency, undercontrolled temperatures without danger to grain from overheating.

I obtain the aforementioned important advantages by means of theapparatus herein described and shown in the accompanying drawings, inwhich Fig. 1 is a side elevation of a apparatus;

Fig. 2 is a vertical section of the drying chamber of the apparatusshown in Fig. 1 along the line AA in Fig. 3;

Fig. 3 is a horizontal section of the drying chamber along the line B--Bin Fig. 2;

Fig. 4 is a vertical section through the lower portion of the dryingchamber and the plenum chamber;

Fig. 5 is a vertical section through the drying chamber of a modifi dform of my invention.

Similar figures of references refer to similar parts in the severaliews.

Moist grain to be dried is received in a hopper I at the top of avertically extending drying chamber 2, at such a rate as to keep thechamber constantly filled with the grain. The grain moves downward bygravity through said chamber and is removed from the bottom thereof at aconstant controlled rate and elevated by means hereinafter described,and is discharged at 3 by grain discharge spout 4. As the grain movesdownwardly in chamber 2, it contacts and passes between horizontalheating pipes 5 adapted to receive and convey a heating fluid, such ashot water or steam, said heating pipes extending transversely of saidchamber in parallel spaced arrangement, the grain also contacting andpass ingbetween vertical heating plates or fins 6 also extendingtransversely of chamber 2 inparallel spaced arrangement and transverselyof pipes 5 and secured to said pipes by welding, brazing or shrinking,etc., wherebythe surfaces of said plates become virtually, for heatconducting purcomplete drying poses, extensions of the outer surfaces ofsaid pipes, thereby providing within a limited space. a relatively largearea for heat conduction to the grain descending between said pipes andsaid plates or fins. and making possiblea high total rate of heattransfer from the heating fluid in said pipes to said grain, with arelatively small difference between the temperatures of said fluid andsaid grain.

The downwardly moving grain in drying chamber 2 is constantly subjectedto the action of an upwardly moving current of air drawn from thechamber. 8 immediately below drying chamber 2. The bottom of dryingchamber 2 is formed of wire netting surfaces 9 of such mesh as to retainthe grain in the drying chamber but permit air to pass freely fromplenum chamber 8 into the grain over nearly the entire bottom of dryingchamber 2. Instead of wire-netting, surfaces 9 may be'of any othermaterial; as for example, perforated sheet metal, adapted to retain thegrain in chamber 2 while allowing air to passfreely into the same fromthe plenum chamber 8. The air passes upwardly through the grain,

passing between heating pipes 5, andheating plates or fins 6, and beingheated by contact therewith, and emerges from the grain into outletflues IDA adapted to extend transversely of the drying chamber, thebottoms of outlet flues IDA being open to the grain, and returns togtheatmosphere through the open ends of said outlet flues.

Grain passing downward through drying chamber 2 and passingbetween andaround airoutlet ducts IDA, into the space below said ducts, en-

' has been heated, partly by heat absorbed by the air from heated grainand partly by heat received directly from portions of heating pipes andheating plates or fins 6. The heating sur face of the heating elementcomprised by pipes 5 and plates or fins 6, is so generally distributedover the cross section of drying chamber 2, as may be noted in Fig. 3,that a large proportion of the kernels in the grain make contact withsome portion ofsaid' heating surface and are forced into intimatecontact with the same by the pressure due to the weight of the grain inthe chamber above said heating element, thereby provid ing conditionsfavorable for rapid conduction of heat from said heating element to thegrain. Each kernel of grain so heated makes contact with the heatingsurface on only a. relatively small proportion of its total perimeter.Much of the remainder of said perimeter is, at the same time, subjectedto the action of the current of air rising through the grain, and istherefore giving up both heat and moisture to said air current. Thethermal conditions provided by, this arrangement are, therefore,favorable to a rapid transfer of both heat and moisture from the grain,to the air. The continuous removal of heat from the grain while itisreceiving heat 'from the heating element, tends to preventtheaccumulation of heat within the'grain and thereby avoids overheating ofthe grain.

The'portion of drying chamber 2 extending between said heating elementand plenum chamber 8 constitutes a heat exchanger in which the heatedgrain and cool air from the atmosphere move in countercurrenh the grainmoving down- ;wardlyand the air upwardly. The downwardly moving heatedgrain gives up heat, in both sensible and latentform; to the upwardlymoving air current, the sensible and latent heat content of theair beingcorrespondingly increased. The temperature of the grain and the vaporpressure of its moisture content, both tend to approach thecorresponding values for the incoming air, the grain being both driedand cooled as it moves downward through'the said space.v

The wire netting surfaces 9 which form the bottom of drying chamber 2and separate said drying chamber from the plenum chamber 8, are

aasaose steeply inclined to right and to left in alternation, forming aplurality of V-shaped troughs, extending in parallel contiguousarrangement. The lower edges of the surfaces 9 which form each suchtrough do not meet but are somewhat separated leaving a narrow slot-likegrain discharge opening ID at the bottom of the trough into which thedried grain descending in chamber 2 I is guided by-the inclined surfaces9 and through which the dried grain exits from said chamber.

'Each discharge opening I0 is connected to a plurality of graindischarge hoppers H which receive the dried grain issuing from dryingchamher 2 through openings I0 and guide said grain into closed grainspouts I2 which extend through the bottom l3 of plenum chamber 8. Thelower end of each spout i2 is provided with a grain discharge wheel I4of conventional type adapted to discharge grain at a controlled ratedetermined by the rate at which said wheel is rotated. Wheels M arecarried upon and rotated by shafts 15 which are driven at a controlledspeed by means hereinafter described. Wheels 14 dis- 'charge the driedgrain into trough l6.

conveyor ll, operating in trough l6 conveys the dried grain to the footof dried grain elevator i8 which elevates the grain and delivers it intograin discharge spout 4, the dried grain being discharged at 3.

Air vent openings i9 are provided in the walls of spouts 12 below thebottom R3 of plenum chamber 8, said openings being adapted to permit thefree escape to the atmosphere of such air as may be forced through thegrain in hoppers l i and spouts 12 by the pressure of air in plenumchamber 8, thereby preventing the building up in spouts l2 of airpressure which might affect the delivery of grain by wheels Hi.

The drying apparatus shown in Fig. l is arranged for utilizing water asthe heating fluid circulated through the heating pipes in the dryingchamber. As shown in that figure, the water is heated in boiler 20, of aconventional type, and is circulated by circulating pump 2| through saidboiler 20, flow pipe 22, flow header 23, heating pipes 5, return header24 and return pipe 25, back to pump 2|. The heating system being of 1the closed type is conventionally equipped with (ill rate of flow of thehot water through heating pipes 5 in drying chamber 2 may be regulatedby valve 3| in return pipe 25, and the temperature of the hot waterobserved by thermometer 30, and regulated as required by manipulation ofconventional draft controls of boiler 20. Water is supplied to theheating system when required through water supply valve 32 and watersuppl; pipe 33, extending from a suitable source, not shown. Drain valve34 permits the heating sys tem to be drained, when required.

While I prefer to employ hot water as the neating fluid circulatedthrough heating pipes it is evident that any other heating fluid, suchas.

' for example, steam, could be similarly employed without departing fromthe essential principle of my invention.

The moving members of the drying apparatus are operated by electricmotor 35, which drives countershaft 36 by means of belt 3?. Instead ofthe electric motor 35, the moving members be driven by any othersuitable means as, for example, an internal combustion engine. Fromcountershaft 36, fan 7 is driven by belt 38, the dried grain elevator 18by twisted belt 39, and

Spiral 2,838,089 circulating pump 2! by belt 40. Spiral conveyor I! isdirectly connected to the shaft, not shown,

carrying the bottom pulley of elevator 18 and receives its motiontherefrom.

Grain discharge wheels l4 chain 4!, speed changing transmission 42 andchains 43 and 44 driving sprocket wheels 45 on shafts i5. Transmission42 is of a conventional type, having speed adjusting means, such as ahandwheel 46, by operation of which the speed of wheels l4 may be variedas required.

In operation, in drying grain, the rate of flow of hot water throughheating pipes 5 is controlled by adjustment of valve 3|, the temperatureof the hot water regulated by adjustment of conventional draft controlsof boiler 20, the rate of movement of the grain through the dryingchamber is controlled by adjusting the speed of the wheels I4 throughmanipulation of handwheel 46, and the volume of air forced upwardlythrough the grain in the drying chamber, is controlled by adjustment ofshutter 41 on intake of fan 1.

I have found it essential to the proper periormance of my drier toemploy fins or plates 6 in addition to having two rows of pipes 5. Thesefins or plates 6 should be properly spaced at substantially 24 per foot.

Under an alternative application of my invention, shown in Fig. 5, I mayarrange heating pipes in a plurality of banks, as for example, in threebanks, 48,49, and 50, each of said banks comprising heating pipes 5,heating plates or fins 6, flow header 23 and return header 24, connectedand arranged, as hereinbefore described, said banks being positioned,one above another in said drying chamber 2, but separated, one fromanother, by intervening spaces, 5| and 52 in said chamber. I have foundthis arrangement to be advantageous where grain of high moisture contentis to be dried and its moisture content reduced in relatively largeproportion, requiring a correspondingly large amount of heat in relationto the quantity of grain handled. This modification of my inventionenables relatively large are driven through reductions to be made in themoisture content of grain, with a less total expenditure of heat than isrequired with heating pipes in a single bank, thereby accomplishing thedrying at a higher thermal efficiency with less tendency to overheat thegrain.

While I have shown three banks of heating pipes, it is to be understoodthat I do not limit myself to this particular number of banks, since itis evident that my invention may be practiced with any other number ofsuch banks without departing from the essential principle of myinvention.

While grain drying apparatus has been employed having horizontal heatingpipes in vertically extending drying chambers in connection with meansfor forcibly passing currents of air upwardly through the grain in saidchambers, I have found that such structure is not adapted for the typeof apparatus which has a capacity for high moisture removal; high ratioof heat conducting surface area to the volume of grain to be handled,and a high rate of moisture removal without subjecting the grain todangerously high temperatures; and, the combination of these features ina compact, portable apparatus as hereinbefore described.

Having thus described by invention, what I claim for Letters Patent is:

A grain drier comprising a vertically elongated chamber adapted to befilled with a column of grain, means for introducing grain into the topof said chamber, a foraminous support for the column of grain at thebottom of the chamber, means for forcing air into the chamber belowtheforaminous support, whereby the air will pass upward through saidsupport and through the column of grain, controllable positive means forremoving grain from said support to the exterior of the chamber, and aradiator in said chamber above said support, said radiator havingmembers spaced to permit the column of grain passing therebetween to beuniformly heated.

GEORGE J. BURKHARDT.

